Electrowetting phenomenon is that a contact angle between an electrolyte solution and an insulating layer changes under an action of an electric field, that is, the electrolyte solution contracts or expands on a surface of the insulating layer under the action of the electric field. An electrowetting display device utilizes the electrowetting phenomenon to display and, by means of electrodes, controls expansion or contraction of oil ink to display. The electrowetting display technology is more and more favored by people because of its features of bistable state display, good reflectivity, low power consumption, wide temperature range and fast enough response speed. The electrowetting display technology at present is still at its preliminary stage, but its demonstrated superior performance and development potential indicate that electrowetting displaying will become an important display method in the field of display technology in future.
FIG. 1A and FIG. 1B show schematic sectional views of an electrowetting display device in the prior art. As shown in FIG. 1, the electrowetting display device in the prior art comprises an electrode 1, a dielectric layer 2 (having a hydrophobic surface), an oil ink layer 3 and a saline solution layer 4, which are disposed between an upper substrate and a lower substrate (both not shown). The electrode 1 is disposed on the lower substrate, the dielectric layer 2 is disposed on the electrode 1, the oil ink layer 3 is disposed on the dielectric layer 2, and the saline solution layer 4 is disposed on the oil ink layer 3. The oil ink layer 3 is colored, and the saline solution layer 4 is transparent.
In one pixel, when no voltage is applied, as shown in FIG. 1A, the oil ink layer 3 is flatted or tiled as a flat thin film on the dielectric layer 2; therefore the pixel is presented as a colored pixel point. When a voltage is applied between the electrode 1 and the oil ink layer 3, as shown in FIG. 1B, the tension of the contact surface of the dielectric layer 2 with the oil ink layer 3 will changes, the result is that the original static state in the pixel becomes no longer stable, and the oil ink layer 3 is moved to one side of the pixel, so that the pixel become a partially transparent pixel point. In the electrowetting display, the oil ink layer 3 may have two functions, including: 1. acting for shielding: in black-and-white display, the oil ink layer 3 is used for shielding and is generally black; 2. acting for displaying: in color display, the color that the oil ink layer 3 by itself is used for display. However, as shown in FIG. 1B, in color display, although the oil ink layer 3 in contraction lets most of the pixel region be exposed, it still shields part of the pixel region, and therefore the display cannot render a satisfying full-color display effect for users.